LOL, right. Many moms-to-be eat whatever they can for the first few months (what up, saltine crackers and Swedish fish?) thanks to a little thing called morning sickness and a hyper-sensitive nose.

And that, kids, is exactly why prenatal vitamins were invented.

What exactly are prenatal vitamins?

Prenatal vitamins are there to fill in any nutritional gaps and make sure there is an abundance of all the vital nutrients your baby needs to grow—especially magnesium, zinc, calcium, vitamins B and C, and folate, says G. Thomas Ruiz, M.D., ob-gyn at MemorialCare Orange Coast Medical Center in Fountain Valley, California.

Supplemental folate, in particular, is very important as it’s been shown to reduce neural tube defects in babies, and you need at least 400 micrograms a day, according to the World Health Organization.

Most of these vitamins are water soluble, meaning you’ll just pee out any excess, says Ruiz. (A.k.a. you don’t need to worry about OD’ing.) There is one exception to this rule, however: iron, which can be toxic in large doses.

Pregnant women need 30 to 60 milligrams of iron each day, according to the guidelines from the World Health Organization. Most prenatal vitamins come fortified with extra iron, so as long as you’re sticking to what’s in your daily prenatal (and not supplementing with even more iron), you’ll be fine, says Ruiz. (Caveat: If you are anemic, you might need even more than that, so discuss your individual needs with your doctor, says Ruiz.)

Okay, so when do I need to start taking prenatal vitamins—and for how long?

Ideally you should start taking them as soon as you start trying to conceive, says Ruiz. (FYI: It’s a myth that they will increase your fertility, though.) Your baby will needs those extra nutrients from the moment of conception, says Ruiz.

Continue to take the vitamins throughout your pregnancy and afterwards, for as long as you’re breastfeeding, he advises.

So how do I choose the right prenatal vitamins? (So. Many. Options!)

Sifting through drugstore shelves or Amazon suggestions is super intimidating. So here are the best-selling prenatal vitamins on Amazon—plus, insight from docs as to whether they really work:

1. One A Day Women’s Prenatal Multivitamins

This is the most popular brand of prenatal vitamins on the market, and it’s a solid choice, says Hillary Wright, M.D., R.D., director of nutrition counseling at Boston IVF and an expert in prenatal nutrition.

It’s not necessarily fancy, but it gets the job done for a reasonable price and, best of all, it’s been verified by an independent lab so it actually contains what it says it contains, she adds. (Which isn’t always the case with supplements as they’re not monitored by the FDA.)

2. Nature Made Prenatal + DHA 200 mg Multivitamin

The best thing about this prenatal vitamin: a large dose of DHA, a fatty acid crucial to fetal brain development, says Wright.

“A lot of prenatals advertise they have this but they have a miniscule amount—you want a minimum of 200 mg of DHA per serving ,” she says. You can also get DHA by taking a separate fish oil supplement.

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3. Vitafusion Prenatal Gummy Vitamins

This is the most popular chewable prenatal on the market for good reason—it has quality ingredients and it tastes good, says Wright.

There is one downside to all gummy vitamins, however: The gummy ingredients (including sugar) displace some of the vitamins. So if you want to make sure you’re getting the most nutrition for your money, stick to the pills, she says.

4. Rainbow Light Prenatal One Multivitamin

This super-popular prenatal vitamin is also one of the priciest—but it might be worth it, says Wright. The brand is known for its high quality and it includes prebiotics and probiotics to help keep your gut bacteria (and therefore, you) happy.

These extras aren’t necessary, and are best gotten through food, says Wright, but they may be a good addition for some pregnant women, especially if you’re struggling to get enough fiber, she adds.

5. Mama Bird Prenatal Multivitamin

These vitamins contain “methylated folate”—a new buzzword in the prenatal vitamin world. Folate is one of the most important vitamins in prenatal pills, but some women have a genetic condition that makes it hard for their bodies to convert the folic acid in most prenatals to the active form the body can use, says Wright.

Here’s the issue: You can’t know that you have the condition unless you’ve had genetic testing done. So if you want to be super-safe and cover all your bases, then a methylated version of folate might be worth the money, she says. Still, she emphasizes that for the majority of women the regular (and more affordable) variety is just fine.

6. TheraNatal Complete Prenatal Vitamin & Mineral Supplement

This prenatal is Wright’s personal favorite and the one she recommends to her clients. It contains iodine and choline—two minerals vital to hormone regulation, fetal growth, and brain development—that are often missing from other prenatal vitamins.

Ideally, you want 150 micrograms of iodine and 450 milligrams of choline every day, she says. They’re also independently tested and have a high standard of quality, she adds.

There is one major downside: They don’t come cheap. These are by far the most expensive on the list, although you may be able to get them cheaper through your doctor or buying them direct from their site.

7. Ritual Prenatal Vitamins

[TK Photo]

These vitamins are a pick because of what they don’t have: calcium. “Calcium and iron compete with each other for absorption,” says Alyssa Dweck, M.D., in Westchester County, New York. “I recommend getting iron from a vitamin and calcium from your diet,” she says, since it’s much easier to get calcium from foods than iron.

These vitamins’ minty favor is a nice bonus for women experiencing morning sickness, as mint is known to control nausea, Dweck added.

8. Pure Encapsulations Prenatal Nutrients

This vitamin is a good option because it contains the methylated types of folate and B12 (again, many pregnant women carry a genetic mutation that doesn’t allow the body to convert folate and B12 into forms usable in the body, says Felice Gersh, M.D., a board-certified ob-gyn and director of Integrative Medical Group of Irvine in Irvine, California).

“If the body can’t properly convert these to the usable vitamin forms then it’s as though none is taken, or worse,” she says. “Unless a woman has had the genetic testing to know what her body can do and can’t do, the stakes are too high in pregnancy to use the cheap forms of these vitamins.”

9. Thorne Basic Prenatal

According to Gersh, this is another great choice because it also contains the methylated forms of folate and B12. It also has more even more folate (a full milligram) than most vitamins out there, which makes it ideal for women who don’t get enough green leafy vegetables into their diet.

“This vitamin is also high in vitamin D and provides a healthy blend of calcium citrate and malate, though it does take three capsules daily though to get these amounts,” she says.

This prenatal vitamin isn’t as pricey as some of the others we’ve mentioned, but it’s definitely a solid choice. In addition to being a good source of vitamin D, it also offers a blend of Vitamin A precursor carotenoids, and also contains ginger, probiotics and an organic vegetable blend.

“This is a great option for women looking for a very affordable option without any unhealthy binders and fillers,” Gersh says.